The present invention relates to a coupling device with a reflecting surface for the coupling into and/or coupling out of electromagnetic waves into and/or respectively out of, for example, optical wave guides, and a method for manufacture thereof.
The present invention relates to a coupling device with a reflecting surface for the coupling into and/or coupling out of electromagnetic waves into and/or respectively out of, for example, optical wave guides, and a method for manufacture thereof.
In particular in telecommunications and data communications, it has become usual to transmit information optically, that is to say, for example, via optical guides. Optical guides are rods or thin fibres of highly transparent optical materials that transmit light by means of multiple total internal reflection along their longitudinal direction. The light generally entering via a flat and/or respectively polished input surface follows all the bends of the fibre, and in the end emerges once more from an again generally polished end surface. After suitable modulation, the electrical signals that have to be transmitted are converted by means of an electro-optical converter into light signals—mostly in the infra-red range, are coupled into the optical wave guide, transmitted by the optical wave guide, and in the end converted back into electrical signals by means of an opto-electrical converter. In order to increase the rate of transmission of the optical wave guides, it has become usual to transmit several different communication signals simultaneously via one optical wave guide. For this, the communication signals are modulated. Different carrier frequencies are used respectively for the different communication signals, so that the individual signals can also be described as wave-coded signals. After transmission of the individual communication signals via the optical wave guide, the individual signals have to be separated and demodulated.
Devices are thus known in this technical field for adding and selecting wavelength-coded signals (light of a specific wavelength or specific wavelengths). Such devices employ optical fibres that have a high information carrying density. The purpose of the devices is to separate out appropriate information or respectively an appropriate wavelength from the large amount of information transmitted. Narrow band filters, for example, can be used for this separation, which allow certain light frequencies to pass almost unhindered, while selected frequencies are reflected. When the light emerges the glass fibre, however, there is inevitably expansion of the beam, which leads either to the intensity at the imaging point, that is to say the point at which the filtered light is plotted, being significantly reduced, or the use of appropriate lens systems, for example, gradient refractive index lenses (GRIN lenses) being necessary in order to collimate the light onto the appropriate imaging point.
The embodiment with the lenses has the disadvantage, however, that it is on the one hand very expensive, on the other hand very accurate alignment is necessary, and moreover, the imaging characteristics are still wavelength-dependent. Alignment has most often to be undertaken in a complex manner by hand, as the core diameter, for example, of the single-mode optical fibres, is only approximately 9 μm. There is therefore a need for a coupling device without the disadvantages described.
The inherent characteristic of glass fibres is that they cannot be routed or respectively bent in any manner required. It is not possible, for example, to bend glass fibres with a radius smaller than approximately 20 to 30 mm, as losses then become too great as in part the criteria for total internal reflection are no longer satisfied. Furthermore, if the curvature is too great, cracks and stresses can form within the material. Appropriately large routing loops must therefore be set out that do, however, take up a significant amount of space in the optical apparatuses. There is also a need for a possibility for routing the optical information flow in the most confined space possible